Heretofore, a torque sensor described in Patent Literature 1 has been mentioned as a technique concerning a joint structure, which fits a cylindrical member to a shaft member such as a solid shaft or a hollow shaft, and crimps the cylindrical member to then fix the cylindrical member to the shaft member.
As illustrated in FIG. 13, in the torque sensor of Patent Literature 1, plural axial grooves 111 extending in an axial direction and a circumferential groove 112 continuous in a circumferential direction are formed on an outer circumferential surface of a large-diameter portion 103A of an end portion of an output shaft 103.
The axial grooves 111 are formed over both end portions of the large-diameter portion 103A. The circumferential groove 112 is formed near a position where an end portion of a cylindrical member 110 is located when the cylindrical member 110 is fixed.
Plural hemispherical projections 113 are formed on positions slightly protruding from a lower end portion of an inner circumferential surface of the cylindrical member 110. The number and the forming position of the projections 113 correspond to those of axial grooves 111. The height of the projections 113 is equal to the depth of the axial grooves 111.
In fixing the cylindrical member 110 to the large-diameter portion 103A, the projections 113 are fitted into the axial grooves 111 to position the cylindrical member 110 in the circumferential direction with respect to the output shaft 103. Next, the cylindrical member 110 is pushed such that the end portion of the cylindrical member 110 comes close to the circumferential groove 112. In such a state, the end portion of the cylindrical member 110 is crimped inwardly so as to bite into the circumferential groove 112.
As described above, in the technique described in Patent Literature 1, the projections provided on the cylindrical member are fit into the grooves provided on the shaft member to prevent displacement in a rotational direction.